TroSim: New Haptic Simulator for Trocar Insertion Procedure

Introduction & ObjectiveTrocar insertion is one of the most cited causes of surgical injuries when performing laparoscopic procedures. Between 1997 and mid-2002, the FDA received about 1,300 laparoscopic trocar-associated injury reports, including reports of 30 fatalities. This process is highly dependent on force feedback with little or no visual feedback. Currently no computer based simulator exists for learning skill. In this paper we describe a new system for training trocar insertion procedure using haptic and visual feedback call TroSim.

DescriptionWhile designing TroSim, a number of things were considered in order to realistically simulate tissue deformation and trauma, including haptic behavior and advanced visualization techniques (figure 1). To obtain exact deformation of the thorax area, data was collected by inserting trocar on a pig model. A force/torque sensor (NANO 25, ATI Industrial Automation, Inc.), mounted at the end effector of a 6 DOF Phantom Omni (Figure 2), was used to measure force and torque from a 12 mm. pyramidal-blade reusable trocar (Intuitive Surgical, Sunnyvale, CA, USA). From the experimental data, the associated force and torque profiles (Figure 3) were computed. The profiles are then spatially aligned, resampled and used for modeling the haptic feedback. To simulate the abdomen tissue the underlying visualization uses a number of spheres connected by virtual springs which simulate the behavior of deformable tissue. In the simulator PHANTOM Premium 1.5/6DOF is used since the trocar insertion simulator needs torque feedback along with 3DOF force feedback. The proposed system consists of a 3D scene and 2D menu, as shown in figure 4. The 3D scene consists of the human body and trocar, and sub windows are included to give many different viewports to show the underlying organs. The 2D menu can be used to control the system and edit haptic properties (stiffness, friction and the coefficients of trocar force profiles) if necessary.

fig1. Schematics of the simulation

fig2. Data collection

fig3. force profile

fig4. Trocar Insertion simulator

Results & ConclusionWe carried out preliminary evaluation of how people learn the trocar procedure with a haptic based TroSim. The evaluation was performed by 9 non-medical subjects without trocar experience. The experiment contained three methods. The first method used a mouse, the second a 6 DOF haptic device without force feedback and the third used the same haptic device with force feedback. Each subject attempted nine trocar insertions, at each of three different modeled insertion points, with each test method. The rate of success was 55% (1st method), 70% (2nd method) and 92% (3rd method). Time to reach peak force for each method was 11.7 s, 6.8 s and 6.39s (p = 0.0047). Thus, haptic force feedback helped users improve their success rate and reduced the time to reach the peak force. We will also evaluate our system with surgeons and medical students and personnel in the future. In conclusion, we have described creating a haptic simulator for trocar insertion called Tro-Sim.

AcknowledgementsThis work was in part funded by the Roswell Park Alliance Foundation and National Science Foundation.